Illuminator, especially a runway approach flashlight

ABSTRACT

The invention relates to an illuminator, especially a runway approach flashlight, for forming a directable, generally rectangular light beam, comprising a light source, such as a xenon lamp, an illuminator body (1), and a reflector supported to it and comprising a generally cup-like rear reflector (2) fitted behind the light source, and means for directing the light beam. To achieve a light beam of a desired shape and to enable it to be directed, the reflector further comprises an ellipsoidal counter reflector (3) fitted in front of the light source, the main axis of the counter reflector being substantially parallel to the shorter side of the light beam, and the reflector (2, 3) is supported to the illuminator body by means of joints (11), so that the reflector can be tilted with respect to the illuminator body (1).

BACKGROUND OF THE INVENTION

This invention relates to an illuminator, especially a runway approachflashlight, for forming a directable, generally rectangular light beam,comprising a light source, such as a xenon lamp, an illuminator body,and a reflector supported to it and comprising a generally cup-like rearreflector fitted behind the light source.

Finish Published Specification 66074, for instance, discloses anilluminator of substantially the above-described type for similarpurposes. The runway approach flashlight according to the inventionshould radiate a flashing light so as to form a beam having the shape ofa horizontal rectangle in cross-section. This beam has to be directed ata predetermined angle with respect to the horizontal plane. Within thearea of the beam, the effective light intensity values have to beadjustable in compliance with various specifications both as concernsthe width of the beam and the maximum/minimum ratio of the intensities.In the above-mentioned known arrangement, the illuminator with itscasing has been made tiltable for directing the beam by providing theback portion of the casing with a joint with respect to which the frontedge of the casing can be lifted by means of an adjusting screw. Thisway of adjustment requires that the electronics controlling theilluminator unit should be placed in a housing separate from theilluminator in order that the tiltable structure would not be too heavyand clumsy. On the other hand, the directing of this kind ofilluminator, that is, the adjustment of the angle of tilt, has to bechecked at least after the illuminator has been installed e.g. on alight support possibly several meters above the surface of the earth. Inthis known arrangement, the light beam itself is shaped by an ellipticalrear reflector and optical means positioned in front of a light source.The light distribution in the illuminator is fixed and cannot beadjusted in compliance with various specifications, but possible changesin the distribution of light have to be made by modifying the structureof the illuminator unit itself.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an illuminator inwhich the light beam is more easily and more simply adjustable in bothshape and direction than in the illuminators known from the prior art.This is achieved by means of an illuminator according to the invention,which is characterized in that the reflector further comprises anellipsoidal counter reflector fitted in front of the light source, themain axis of the counter reflector being substantially parallel to theshorter side of the light beam.

The arrangement of the invention also provides an illuminator in whichthe illuminator casing need not be tilted for directing the light beambut the light beam is directed by tilting only the reflector and thelight source supported to it.

Two prismatic refraction plates of transparent material are supportedpreferably to the rear reflector, substantially in the plane of itsmouth, in such a way that they cover the mouth of the rear reflectorwith the exception of a substantially centrally positioned area ofuniform width. By means of these prismatic refraction plates, both thedimensions and the intensity distribution of the rectangular light beamemitted by the illuminator can be varied. Preferably, the refractionplates are supported to the rear reflector so as to be adjustable. As tothe maximum/minimum ratio of the light beam intensities, it ispreferable that light can be guided to the corner areas of the primarybeam by means of the refraction plates, whereby the refracting angle ofthe refraction plates may be about 15° and the directional angle withinthe range from 2° to 5°. The width of the area of uniform width betweenthe refraction plates also affects substantially the maximum/minimumratio of the intensities.

Furthermore, it is preferable that the rear reflector be divided intothree sections substantially parallel with the longer side of the lightbeam in such a way that when light beams emitted from the light sourceand returned from the front reflector are reflected from the twooutermost sections, they are directed sidewardly, forming an acute anglewith respect to the light beams reflected from the middle section. Inthis way, the light reflected from the rear reflector can be spreadoutward within its edge areas, and the length of the longer side of thelight beam having a rectangular cross-section. That is, the width of thelight beam can be adjusted to some extent by the selection of theabove-mentioned acute angle. This acute angle is preferably about 6°.

In order to be able to direct the light beam in the illuminatoraccording to the invention with respect to the horizontal plane moresimply than previously, the reflector is supported pivotally to theilluminator body. It is also to be preferred that the illuminator bodycomprises a levelling means which is arranged to indicate the positionin which the illuminator body is positioned substantially horizontally,and the reflector comprises a scale plate which can be adjustedpositionally with respect to the illuminator body and which indicatesthe angle of tilt of the reflector with respect to the illuminator body.In this way it can be ensured as early as at the assembly stage of theilluminator that the scale plate attached to the illuminator body is inan appropriate position in view of the vertical position of thereflector; at the installation site, the reflector thus only has to betilted at a desired angle of tilt by means of the marks of the scaleplate. Of course, it is thereby assumed that the illuminator body can bepositioned on a horizontal supporting surface, which, on the other hand,can also be checked by means of the levelling means provided in theilluminator body.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the illuminator according to the invention will bedescribed in more detail with reference to the attached drawings, inwhich:

FIG. 1 is a front view of an illuminator according to the invention,that is, as viewed in the direction of the light beam;

FIG. 2 is a cross-sectional view of the illuminator of FIG. 1substantially at right angles to the light beam,

FIG. 3 is a front view of a refraction plate contained in the reflectorof the illuminator;

FIG. 4 is a side view of the refraction plate of FIG. 3; and

FIG. 5 shows an arrangement comprised in the illuminator according tothe invention for adjusting the angle of tilt of the reflector.

DETAILED DESCRIPTION

The illuminator according to the invention shown in FIG. 1 comprises anoutermost water-proof casing 7 the front surface of which is transparentand which encloses the reflector means of the illuminator, and, ifrequired, also the electronic means controlling the illuminator. This ispossible as the illuminator casing can be positioned steadily on theunderlying surface and need not be tilted for directing the light beam.The illuminator itself comprises an illuminator body 1 having a baseportion and column-like portions projecting upwardly from the baseportion, a reflector and an associated light source being supported onthe column-like portions. The reflector comprises a generally cup-likerear reflector 2 which is fitted behind the light source and anellipsoidal counter reflector 3 fitted in front of the light source. Themain axis of the counter reflector is vertical, that is, parallel to theshorter side of the light beam, and the counter reflector furthercomprises a central opening 8 for allowing the passage of light emittedfrom the light source straight in the right direction. The rearreflector 2 is formed of a blank having the shape of a paraboloidgenerated by rotation and divided into three vertical sections 2A, 2Band 2C. The division is carried out in such a way that light beamsoriginating from the light source and reflected from the two outermostsections 2A and 2C are directed sidewardly, thus forming a smallishacute angle with respect to light beams reflected from the middlesection 2B. This smallish acute angle may be e.g. about 6°. Furthermore,two prismatic refraction plates 4 of transparent material are supportedto the rear reflector 2, substantially in the plane of its mouth, insuch a way that they cover the mouth of the rear reflector 2 with theexception of a substantially centrally positioned area of uniform width.The width of this area is a and its longitudinal axis is parallel to thelonger side of the rectangular light beam of the illuminator. Thedistance a should be adjustable. By way of example, FIG. 1 shows asimple arrangement in which the refraction plates 4 are supported to therear reflector 2 by means of screws 9 in such a way that the screwspenetrate the refraction plates through elliptical openings 10. In thisway the distance between the refraction plates 4 can be adjustedsufficiently.

As already mentioned above, the entity formed by the rear reflector, thecounter reflector and the refraction plates is supported on the columnsof the illuminator body 1 by means of joints 11 provided in the columns,the joints being attached to the rear reflector substantially at theends of its horizontal axis.

FIGS. 3 and 4 show the refraction plate 4 in more detail. As appearsfrom the figures, the prisms of the refraction plate have a directionalangle which is about 2.5° in FIG. 3. This directional angle preferablyranges between about 2° and 5°. In FIG. 4, in turn, the angle ofrefraction of the refraction plates is about 15°. These given anglevalues are not critical but they can be adjusted to some extent incompliance with the specifications imposed on the light beam of theilluminator in each particular case.

FIG. 5 shows an arrangement comprised in the illuminator according tothe invention, which enables the angle of tilt of the illuminator to beset in advance before the installation of the illuminator on a lightsupport or other similar supporting surface. The arrangement shown inFIG. 5 comprises a levelling means attached to the illuminator body 1,such as a water level 5 which enables the illuminator body 1 to bepositioned horizontally. In this position, the reflector structure, inturn, will be positioned vertically, that is, the light beam reflectedfrom it will be horizontal. In this position, a scale plate 6 attachedto the reflector is locked in a position 0° by means of screws 12, asshown in FIG. 5. Thereafter the light beam of the illuminator can bedirected at a desired angle by tilting the reflector so that the scaleplate 6 will indicate this desired angle value at the edge of theilluminator body 1. Thereafter the reflector can be locked in thistilted position by means of a screw 13 bearing against the illuminatorbody 1. In this way the reflector can be tilted reliably in advance atthe desired angle of tilt. This arrangement avoids the use of separate,external directing devices difficult in use in the installation of theilluminator. After the installation, the direction can always be checkedby means of the water level 5. This is because the water level 5indicates if the installation surface of the illuminator is horizontal,whereby the angle of tilt of the reflector is the angle indicated by thescale 6. By means of the scale shown in FIG. 5, the reflector can betilted 3° to 10° upward from the vertical plane, that is, the light beamcan be lifted through a corresponding angle upward from the horizontalplane.

The illuminator according to the invention, especially a runway approachflashlight, is described above only by means of one exemplifyingstructural embodiment, and it is to be understood that the principlesaccording to the invention can be realized by means of other similarstructural arrangements without, however, deviating from the scope ofprotection defined in the attached claims.

I claim:
 1. A runway approach illuminator for forming a directable lightbeam that is generally rectangular in transverse cross-section, so thatsuch cross-section has two shorter sides and two longer sides, saidilluminator comprising:a body; a light source supported on said body andoriented so as to have a front and a rear; a forwardly facing cuppedrear reflector having a mouth opening forwardly from behind said lightsource, and arranged to reflect light generally forwardly; a rearwardlyfacing ellipsoidal counter-reflector, arranged to reflect lightgenerally rearwardly from in front of said light source; said rearreflector and counter-reflector being mounted to said body with saidcounter-reflector having a main axis thereof disposed substantiallyparallel to said short sides of said transverse cross-section of saidbeam.
 2. The illuminator of claim 1, wherein:said light source is axenon lamp.
 3. The illuminator of claim 1, further including:said mouthof said rear reflector is disposed in a plane; two prismatic refractionplates made of transparent material being supported on said rearreflector and being disposed substantially in said plane so as to coversaid mouth but for a substantially centrally positioned area locatedbetween said plates and having a uniform width parallel to said shortsides of said transverse cross-section of said beam.
 4. The illuminatorof claim 3, wherein:said prismatic refraction plates have prismaticrefracting surfaces angled at about 15° to said plane extending atdirectional angles of from about 2° to about 5° from parallelism withsaid short sides.
 5. The illuminator of claim 3, furtherincluding:adjustable supports supporting said plates on said rearreflector, for adjustment towards and away from one another or narrowingand broadening said area located between said plates.
 6. The illuminatorof claim 1, wherein:said rear reflector comprises a central sectionflanked by two opposite outermost sections disposed adjacent one anotherin a direction parallel to said long sides; said central section beingarranged to reflect said light beam along a first axis, and saidoutermost sections being arranged to reflect said light beam alongrespective second axis, which diverge forwardly from said first axis atrespective acute angles, for spreading said light beam.
 7. Theilluminator of claim 6, wherein:said angles are about 6°.
 8. Theilluminator of claim 1, further comprising:a waterproof casing having atransparent front surface, said casing being arranged to be stationarilymounted; said body being located within and stationarily supported onsaid casing; and said light source, rear reflector and counter-reflectorbeing adjustably mounted to said body, so that said light beam can beaimed by tilting said light source, rear reflector and counter-reflectorwhile said casing remains stationary.